Fluid pressure feed and rapid traverse system of transmission of power



April 15, 1941. M KENDRIQK ,EMGQ FLUID PRESSURE FEED AND RAPID TRAVERSESYSTEM OF 'rmwsmssrow OF POWER Filed Feb. a, 1958 Char/e5 lfe/m rlb/f 2d aw/w A TTORNEYS.

Watented Apr. 15, i941- 2,238,060 FLUID PRESSURE FEED RAPID TRAV- ERSEPOWE RSYSTEM OF TRANSMISSION OF Charles M. Kendrick, New York, N. Y.,assignor to Manly Corporation, Washington, D. (3., acorporation ofDelaware Application February s, 1938, Serial No. 189,362

v 6 Claims. This invention relates to systems for the transmission ofpower by means of fluid under pres sure and more particularly to suchsystems in which the driven member is actuated at relatively low speedby fluid under relatively high'pressure',

and at relatively high speed by fluid under relatively low pressure. Thelow-speed-high-pressure actuation of the driven member is frequentlytermed the feed or the slow traverse movement and thehigh-speed-low-pressure actuation is correspondingly termed rapidtraverse; for convenience these terms will be employed in thedescription which follows and the system as a whole will be termed afeed and rapid traverse system."

Systems of this general character have heretoiore been proposed in whichan excess fluid volume is pumped and by-passed during the feed or slowtraverse, viz, systemsin which two constant delivery, constantlyoperating, pumps are employed for supplying the fluid pressure, with thefluid furnished by one pump by-passed back to the source during the feedor slow traverse.

One object of the invention is a novel and improved fluid pressure feedand rapid traverse system in which a single pump, namely a singlevariable delivery pump, is employed as the source of fluid pressure bothfor the feed and for the rapid traverse strokes, and particularly such asystem including a control for varying the delivery of the pump to meetthe exact volume needs of the feed and rapid traverse strokesrespectively without the necessity oi pumping and by-passing excessfluid.

A further object of the invention is a system of the character indicatedwherein the fluid volumes delivered for rapid traverse and for feedrespectively are held steady with no surging or pulsation due to changein the pumps delivery,

and, further, such a system wherein the delivered volume whether thatfor the rapid traverse or for the feed or slow traverse is unaffected byminor variations in operating pressure of the fluid.

A further object is to provide such a system which includes simple,novel and relatively inexpensive control valve mechanism for thevariable delivery pump whereby the volumes of fluid delivered therebyare substantially restricted to the volumes required for feed or slowtraverse and for rapid traverse --respectively, the delivery of the pumpchanging from one to the other of these volumes substantially nstantlyand without interruption, thus limiting the delivery of all othervolumes to those incident to this change.

Other objects will appear from the following description of anillustrative embodiment of the invention which is shown in theaccompanying drawing, wherein- Fig. 1 shows, in partly diagrammaticarrangement, an embodiment of a feed and rapid traverse system accordingto the present invention, certain of the control and power mechanism ofwhich are shown in section, and I Fig. 2 is a detail view.

Referring now to the drawing, the-preferred embodiment of the inventionincludes a variable delivery pump Iii receiving its supply of fluidthrough an inlet conduit Ii from a reservoir it. The pump i0 is alsoprovided with a discharge conduit l3 leading to and connecting with adirectional valve ii of conventional type which controls the directionof operation of the power cylinder I6. The discharge conduit i3 is alsoconnected with a suitable pressure relief valve it which may be employedas a safeguard against excessive fluid pressure-in the system or may beutilized to determine the working pressure of the fluid during feed orslow traverse.

The volume of fluid delivered by the pump Iii is controlled by theposition of a laterally movable adjusting rod or volume determiningelement 20. The arrangement is such that movement of the adjusting rod20 inward (or toward the left as viewed in the drawin causes decrease inthe delivered volume, while its movement outward (or toward the right)causes increase of the volume of fluid delivered. i

Movement of the adjusting rod 20 is effected and its position controlledby power means in co operation with control valve mechanism. In theembodiment here chosen for illustration, the power means is a fluidmotor which includes an adjusting piston 2i reciprocable in an adjustingcylinder 22 and appropriately connected with the adjusting rod 20, asindicated as 23, for simultaneous movement therewith. The adjustingpiston II is moved inward or in a delivery decreasing direction bypressure fluid: admitted to the right hand end of the adjusting cylinder22 through the pipe 24 but is preferably moved outward or in a deliveryincreasing direction by a spring 25. Movement of the adjusing piston 2|,and hence its position, is entirely controlled by admission and exhaustof fluid to and from the right hand end of the adjusting cylinder 2t,thus simplifying the fluid circuit and the necessary control mechanismas will be more fully explained presently. A return pipe 25 leads fromthe left hand end of the adjusting cylinder 22. to the reservoir I2 topermit the passage of any fluid leaking past the adjusting piston 2|from the right hand end "of the adjusting cylinder 22.

Suitable means are also provided to determine the maximum and theminimum fluid volumes to be delivered by the pump Hi. In the presentinstance these delivery determining means are shown as adjustable stops21 and 23 respectively for the adjusting piston 2|. The stop 21 limits{the movement of the adjusting piston 2| and its attached adjusting rod20 in an out'ward'or delivery increasing direction and hence determinesthe maximum fluid volume delivered by the pump l; it is accordingly setso that the maximum volume thus determined is the volume required forrapid traverse. Similarly, the stop 28 limits movement of the adjustingpiston 2| and adjusting rod 20 in an inward or delivery decreasingdirection and hence determines the minimum fluid volume which the pumpl6 delivers; it is therefore set so that the minimum volume thusdetermined is the volume desired for feed or slow traverse. This stop 29comprises a pair of adjustable nuts on a screw threaded part of thepiston rod, and the movement of the piston and rod to the left islimited by the stop 23 engaging with the end wall 28' of the cylinder.

Admission and exhaust of fluid to and from I the adjusting cylinder 22through the pipe 24 are under control of control valve mechanism whichincludes a valve housing 3| in which is a valve bore 32 having anenlarged end 33 (for convenience hereinafter termed the high pressureend). The latter is connected as by a pipe 35 with the discharge conduit|3 from which it .receives a supply of fluid under substantially thesame pressure as that in said discharge conduit l3. The other end of thevalve bore 32 (which for convenience will be hereinafter termed theexhaust end") is connected with the reservoir l2 by means of acounterbore 36 on the end of the valve housing 3| which extends to andconnects with a passage 31 to which the return pipe 39 is suitablyconnected. An annular cylinder port 39 is also'formed in the valve bore32 intermediate the ends thereof and is suitably connected with the pipe24, whose other end is connected with the right hand end of theadjusting cylinder 22 as already stated.v

A valve piston 40 is slidably mounted in the valve bore 32 and is madeof such length that I one of its ends at all times extends into the highpressure end 33 of the 'valve bore 32. The proportions are also suchthat the other end of the waive piston 40 is even with the exhaust endof the valvehousing 3| when said piston 40' is in its extreme workingposition toward the right, as shown in the drawing. The piston 40 isformed intermediate its ends with a singlevalve.

head 4| which eflectively cutsofi communica-, tion between the portionsof the'valve bore 32 on either end thereof and which in the preferredarrangement-is materially wider than the cylinder port 39, for example.several times wider, as in the embodiment illustrated. In order toflrmly guide the valve piston 40 and to prevent binding, a plurality ofguiding surfaces 42 extend I ,/from the head 4| tothe ends of the valvepiston 40, suitable recesses being formed circumferentially'between theguiding surfaces" to permit the passage of fluid. The guiding surfaces42 d intermediate recesses are so arranged that the hydraulic forcesacting in a radial di- -rection on the valve piston 49 at any point arebalanced, in the usual manner.

The end of the valve piston 40 which lies in the high pressure end 33 ofthe valve bore 32 is acted upon by pressure fluid therein which tends tomove the valve piston 43 toward the left, as viewed in the drawing.Maximum movement or the valve piston 40 in this direction is limited bya stop 43, comprising a pin driven through said valve piston 40 near itsend, which is adapted to strike the shoulder 33' formed by themner endof the enlarged portion 33 of the valve bore 32. The arrangement ispreferably made such that the stop 43 does not strike this shoulderuntil the valve piston 40 has moved a distance toward the leftsuflicient not only to connect the cylinder port 39 with thehighpressure end 33 of the valve bore 32 but also to permit over-run oithe valve head 4| a short distance (for example, 1%") beyond the pointwhere this connection is established.

The force acting on the valve piston 40 in a direction tending to moveit toward the left is opposed by a force exerted by a spring 45 actingon the opposite end of the valve piston 40, that is the end thereofwhich is in the exhaust end of the valve bore 32, and urging it towardthe right. The force of the spring 45 is transmitted to the end of thevalve piston 40 by means of an intermediate end piece 46 of greaterdiameter than the counter-bore 36, so that the adjacent end of the valvehousing 3| acts as a stop for the end piece 46 and limits the distancewhich said valve piston 40 can be moved toward the right by said spring45. The drawing shows the postion of the parts when the end piece 46 isagainst the end of the valve housing 3|, with the valve piston 49 in themaximum position toward the right to which it can be moved by the spring45. The arrangement is such that when the valve piston 40 is in thisposition, the head 4| is to the right of the cylinder port 39 so thatsaid cylinder port 39 is connected with the exhaust end of the valvebore 32, a short over-run beyond the point at which this connection isestablished also being preferably provided in this direction of movementof the valve piston 40. As the valve piston is not attached to the endpiece, 46 it is capable of movement still farther toward the right thanthe position in which it is shown in the drawing; such movement isunlikely to occur but the maximum travel in this direction is limited bythe plug 34 which closes the high pressure end 33 of the valve bore 32,

this stop being provided to assure that the head 4| will at all times bein the valve bore 32.

The spring 45 is enclosed by a housing 41, one end of which is suitablyconnected to the valve housing 3|, as by the screw threaded-connectionshown, and the other end of which is closed by a plug 48. A screw 49extends through the plug 48 and provides means for adjusting the com:pression of the spring 45, the screw 49 abutting against an abutmentmember 50 in engagement is relatively low so that the force which itexerts on the exposed end of the valve piston 40 is insuflicient toovercome the opposing force of the spring 45 and the parts assume theposition shown. The valve piston 40 is then in its ex-' treme workingposition toward the right and its head 4| is to the right of thecylinderport 39. The cylinder port 39 is thus connected with the exhaustend of the valve bore 32, so that fluid may-be exhausted from the righthand end of the adjusting cylinder 22 through the pipe connection 24,the bore 32, the counterbore 36, the passage 31 and the pipe 38 to thetank l2. The adjusting piston 2| and adjusting rod 20, under action ofthe spring 25; are moved to their extreme outward or delivery increasingposition as determined by'the stop 21 and are held in this position aslong as the fluid in the discharge conduit l3 and high pressure end 33of the valve bore 32 remains under low pressure, as is the case duringrapid traverse. The pump III is thus caused to deliver its maximumvolume, as determined -by'the stop 21, under relatively low pressure forrapid traverse.

The resistance presented by the power cylinder IE will immediatelyincrease to a. relatively high amount upon completion of rapid traverseand the beginning of feed or slow traverse, causing a correspondingimmediate increase in the pressure 01' the fluid in the dischargeconduit i3 and the high pressure end of the Valve bore 32. The forceexerted by this relatively high pressure fluid on the end of the valvepiston 40 overcomes the resistance presented by the spring 45 and movesthe valve piston 40 to position toward the left, in which position thevalve head 4| is to the left of the cylinder port 33. The high pressureend of the valve bore 32 is thus connected with the cylinder port as sothat pressure fluid is admitted to the right hand end of the adjustingcylinder 22. The adjusting piston 2| is immediately moved inward or in adelivery decreasing direction as far as permitted by the stop 28. Thismovement of the adjusting piston 2| causes similar movement, of course,of the adjusting rod 2|! so that the volume of fluid delivered by thepump It! is reduced to the minimum determined by the stop 28 and is heldin this minimum delivery position as long on the end of the valve piston40 in the high its working pressure endof the valve bore 32 remainsrelatively high, as will be the case throughout feed or slow traverse.

The pressure of the fluid in the discharge conduit I3 and hence in thehigh pressure end of the valve bore 32 will again drop to a relativelylow amount upon completion of feed or slow traverse and the beginning ofrapid traverse.

immediately upon this pressure'drop, the valve piston 40, the adjustingpiston 2| and adjusting rod 23 will be returned to their positions asshown and the fluid volumedelivered by the pump M will thus immediatelybe increased to the'maximum determined .by .the stop 21.

The control valve and power adjusting mechanism of the presentinvention-therefore act cooperatively to efiect delivery of the maximumas the pressure of the fluid acting volume of fluid at low pressure forrapid traverse and to, effect delivery of minimum fluid volumeat'relatively high pressure for feed or slow trav erse. The change frommaximum to minimum volumeaor vice verse, is made responsive to change inthe pressure of the working fluid in .the dischargeco'nduit l3and,'while described variations in the mum as discharge conduit i3 isequal to or greater than variation from one to the other of theseextreme amounts, which is practically negligible. By adjustment of thestops 21 and 28, the maximum and minimum fluid volumes may be made suchas to produce the desired rates ofmovement of the power cylinder I6 forrapid traverse and for feed or slow traverse respectively. Likewise, byadjustment, of the compression of the spring 45 the pressure of thefluid in the discharge conduit I3 required to efiect the shift frommaximum to minimum volume, or vice versa. may be varied and controlled.

The feed and rapid traverse system of the present invention has numerousadvantages. It makes possible, for example, the use of one variabledelivery pump instead of two constant delivery pumps, such as arefrequently employed for this purpose. It reduces the necessity forby-passin-g fluid during feed or slow traverse and can be so adjustedthat by-passing is entirely eliminated; this saves power and avoidsheating and churning of the fluid, w ch is usually oil. It ise'iilcient, reduces to a minimum the power required to supply the neededactuating fluid and one-half H. P. will drive the pump to deliverapproximately four and one-fourth gallons per minute of fluid at 1,000lbs. per sq. in. pressure for feed or slow traverse and approximately 17gals. per minute at 250 lbs. per sq. in. pressure for rapid traverse.

Another important advantage of the system of the present invention isthat the volume delivered both for rapid traverse and for feed or slowtraverse are held steady without surging or pulsation due to change inthe pumps delivery. There is no "hunting and the delivered volume is notaffected by minor variations in operating pressure of the fluid in thedischarge conduit l3. This is due to the fact that the pumps deliveredvolume is maintained at maximum whenever the pressure in the dischargeconduit 3 is below the amount necessary to move the valve piston 4 0against the spring 45 39 with the high pressure end 33 of the valve bore32. The valve piston 40 is free, of course.

to move toward the left to some extent under lower pressures, but theconnection between the cylinder port 39 and the valve bores highpressure end 33 cannot be established until the piston head 4| has beenmoved to the left of said cylinder port 39, and this cannot occur untilthe pressure of the fluid reaches an amount determined by the setting ofthe spring 45. Minor pressure below this amount do not, therefore, haveany efifect on delivery. Similarly,the delivery of the pump will be heldsteadily and continuously at minilong as the pressure of the fluid inthe the amount, as determined by the spring t5, necessary to connect thecylinder port 39 with the valve bores high pressure end 33, regardlessof variations in the pressure above this amount. The extra width of thevalve piston head 4|, as compared to thewldth of the cylinder port forexample,

the pumps 39, thus prevents change of the existing connection betweenthe end of the adjusting cylinder 22 and the cylinder port 39, from thefluid pressure admission connection to the exhaust connection, or viceversa, upon small fluctuations of the pressure in the discharge conduitl3 and thereby assists 'in eliminating any hunting" tendency. Thepressure employed for feed or slow traverse is usually substantiallyhigher than that used for rapid traverse so that there is no diflicultyin setting the spring 45 to bring about the shift from maximum volume tominimum volume, or vice versa, at a satisfactory intermediate pressureand, if desired, the difference in pressures necessary to effect thisshift may be held within a relatively narrow range, as by making thespring 45 with a low rate (i. e., such that a relatively small addedincrement of load is required to produce a given amount of totaldeflection-of the spring).

In addition to the operating advantages which it makes possible, thenovel construction of the control valve mechanism also results in easyand relatively inexpensive manufacture. Only one close fit is requiredin its entire structure and that is the relatively simple one of fittingthe valve piston 40 into the valve bore 32. The valve head 4| andguiding surfaces 42 are of the same diameter so that the valve piston 40may be readily ground from end to end to the proper size.

No other precise sizes are required anywhere in the structure andordinary machining tolerances, such as .010" or i%4", may be otherwiseused throughout. For example, it is not necessaryto hold the length ofthe valve bore 32 or of the valve piston 40 to a precise-dimension.Likewise, there is' no exact requirement either as to the width (i. e.axial length) of the cylinder port 39 and valve head 4| or as to theirrelative positions in the valve bore 32 and on the valve piston 40respectively. Minor variations' in size or relative position of theseparts merely aflects the amount of over-run of the valve head 4|. Thewidth of the valve head 4| must, of course, be at least equal to thewidth of the cylinder port 39 and in many instances its width may beconsiderably greater than that i of the cylinder port 39, which is thearrangement illustrated in the drawing; such excess width of the valvehead 4| has no effect on the operation except to increase the pressurerange 7 during which said valve head 4| completely covers the cylinderport 39 and thus cuts off communication between the cylinder port 39 andboth ends of the valve bore 32, thereby assisting in elimination ofhunting, as already explained.

Another feature of this control valve mechanism is that the highpressure fluid is confined to the bore of the short and relativelyeasily made valve housing 3|, in which all fluid connections to and fromthe valve mechanism are also made. This permits the use of inexpensivematerial such as thin steel tubing for the spring housing 41, as itsbore is connected with the exhaust, and also makes it possible to usesimple threaded joints at both ends of the spring hous- It will beunderstood that the foregoing is merely exemplifying disclosure and thatchanges may be made in the apparatus without departing from theapplicants invention as defined in the appended claims.

I claim: 1. In a fluid circulating system comprising a fluid operatedmember having a rapid traverse to efiect the delivery for the slowtraverse stroke,-

fiuid pressure operated means for effecting an instantaneous shift ofsaid device from one of said positions to the other upon transition ofthe fluid operated member from one stroke to the other, stops limitingthe movement of the fluid pressure operated means in both directions fordetermining the deliveries during the rapid traverse and the slowtraverse strokes respectively, said fluid pressure operated meanscomprising a fluid pressure piston operated in one direction by fluidpressure and in the other direction by a spring, and means responsive tothe change in pressure in the discharge conduit upon transition of thefluid operated member from one stroke to the other for controlling saidfluid pressure operated means and causing said instantaneous shifts andfor holding said fluid pressure operated means against movement uponchanges in pressure in said discharge conduit other than changesincident to transition of the fluid operated member from one stroke toanother.

-2.- In a fluid circulating system comprising a fluid operated memberhaving arapid traverse low pressure stroke and a slow traverse highpressure stroke, and a variable delivery pump having a fluid dischargeconduit connected with said fluid operated member and delivering thewhole fluid pressure supply volumes for both rapid and slow traversestrokes, in combination a delivery control and determining device forsaid pump operable to one predetermined position to effect the deliveryneeded for the rapid traverse and to another predetermined position toefiect the delivery for the slow traverse stroke, fluid pressureoperated means for effecting an instantaneous shift of said device fromone of said positions to the other upon transition of the fluid operatedmember from one stroke to the other, stops limiting the movement of thefluid pressure operated means in both directions for determining thedeliveries during the rapid traverse and the slow traverse strokesrespectively, and a fluid pressure operated valve responsive to thechange in pressure in the discharge conduit for controlling said fluidpressure operated means comprising a cylinder one end of which is alwaysin connection with the discharge conduit, said cylinder including anannular port connected with said fluid pressure operated means, a pistontherein provided with a head wider than said annular port, said pistonat low pressures connecting the fluid pressure operated means with theexhaust, at high pressure connecting said fluid pressure operated meanswith the discharge conduit and at intermediate pressures disconnectingsaid fluid pressure operated means from both said discharge conduit andsaid exhaust, and a spring actuating said piston valve in one direction.

3. In a fluid circulating system comprising a whole fluid pressuresupplyvvolumes for both rapid and slow traverse strokes, in combination,a delivery control and determining device for said pump operable to onepredetermined position to eflect the delivery needed for the rapidtraverse and to another predetermined position to eflect the deliveryfor the slow traverse stroke, power actuated means for efiecting aninstantaneous shift of said device from one of said positions to theother upon transition of the fluid operated member from one stroke tothe pressure fluid to said cylinder and the exhaust of fluid therefrom,said valve means including a valve bore having a fluid pressure supplyport, a fluid exhaust port and a cylinder port connected with saidcylinder, said valve means also' including a valve piston movable insaid bore other, and means responsive only to the large changes inpressure in the discharge conduit incident to transition of the fluidoperated memher from one stroke to the other for controlling said poweractuated means and causing said instantaneous shifts.

4. In a fluid circulating system comprising a fluid operated memberhaving a rapid traverse low pressure stroke and a slow traverse highpressure stroke, and a variable delivery pump having a fluid dischargeconduit connected with said fluid operated member and delivering thewhole fluid pressure supply volumes for both rapid and slow traversestrokes, in combination, a delivery control and determining device forsaid pump operable to a predetermined minimum delivery position abovezero and to a predetermined maximum, delivery position, power actuatedmeans for said'delivery determining device holding the latter in one orthe other of said predetermined positions, and means responsive to thechanges in pressure in the discharge conduit due to transition of themember from one stroke to the other for controlling the shifting of thedevice from one position to the other, said last named means having arange of movement responsive to intermediate pressures in said dischargeconduit in which said device is maintained in the position occupiedprior to the occurrence of said intermediate pressures.

5. In a fluid circulating system comprising a fluid operated member anda variable delivery pump having a discharge conduit connected with saidfluid operated member, in combination, a delivery determining device forsaid pump operable to a predetermined minimum delivery position abovezero delivery and to a predetermined maximum delivery position, afluid-pressure piston reciprocable in a cylinder and active to hold saiddevice in said minimum delivery position upon admission of pressurefluid to said cylinder and also active to hold said device in saidmaximum delivery position upon exhaust of fluid from said cylinder, andvalve means responsive to the pressure of the fluid'in said dischargeconduit for regulating the admission 01' responsive to fluid pressure insaid discharge conduit and active to control the admission of pressurefluid to said cylinder port and the exhaust of fluid therefrom, saidvalve piston having one range of movement responsive to relatively highpressures in said discharge conduit in which range said cylinder port isconnected with said fluid pressure supply port, said valve piston havinganother range of movement responsive to relatively low pressures in saiddischarge conduit in which range said cylinder port is connected withsaid exhaust port, and said valve piston also having 'an intermediaterange of movement responsive to pressures in said discharge conduitintermediate said relatively low and relatively high pressures in whichrange said vcylinder port is disconnected from both said fluid pressuresupply port and said exhaust port, whereby said delivery determiningdevice is held in the predetermined delivery position occupied prior tothe occurrence of said intermediate pressures in said discharge conduit.

6. In a fluid circulating system comprising a fluid operated memberhaving a rapid traverse low pressure stroke and a slow traverse highpressure stroke, and a variable delivery pump having a fluid dischargeconduit connected with said fluid operated member and delivering thewhole fluid pressure supply volumes for both rapid and slow traversestrokes, in combination, a delivery control and determining device forsaid pump operable to one predetermined position to efiect the deliveryneeded for the rapid traverse and to another predetermined position toeifect the delivery for the slow traverse stroke, a cylinder and pistonoperated to one position by a spring and to the other position by fluidpressure for efiecting an instantaneous shift of said device from one ofsaid traverse positions to the other incident to transition of the fluidoperated member from one stroke to the other and a second cylinderhaving a port at one end connected with the fluid discharge conduit ofthe pump and another port axially removed from the flrst named port and.in communication with said first named cylinder and a piston in saidlast named cylinder responsive only to the large changes in pressure inthe discharge conduit incident to transition of the fluid operatedmember from one stroke to the other for connecting and disconnecting theports of said second named cylinder, including means for exhaustingfluid pressure from said first named cylinder at pressures in thedischarge conduit below a predetermined value.

CHARLES M. KENDRICK.

